Influence of pregnancy on breast cancer tumor characteristics and mortality in Iowa women

Abstract

584 Background: Hormonal factors such as pregnancy influence development and course of breast cancer. We identified women who became pregnant during the preclinical phase or shortly after diagnosis of breast cancer, compared them with similar women who had not been pregnant in that time period, and studied tumor characteristics and mortality. Methods: Birth and fetal death certificates were linked with Iowa Cancer Registry information for 10,624 women ≤50 years of age diagnosed with breast cancer as a first invasive primary between January 1, 1975 and December 31, 2002. Women who were pregnant two years before (n=160) or after diagnosis of breast cancer (n=53)and those who had not been pregnant (NP) (n=5008) were identified using probabilistic computer matching with manual review confirmation. Clinical, pathological and 10-year survival data were compared between these groups. Preliminary analysis revealed similarities between women who were pregnant before and after diagnosis. These were combined for analysis (P). Results: The study subjects distributed themselves across two SEER stages of disease: 1) localized, and 2) locally advanced or regional nodal disease (LABC). SEER stage (50% LABC vs. 39% LABC) and grade (75% high grade vs. 56% high grade) were higher in P than in NP cases. Ten-year survival for localized disease was 0.766 (95% CI 0.649–0.848) for P and 0.874 (95% CI 0.858–0.888) for NP (log rank test p= 0.0178). Ten-year survival for LABC was 0.520 (95% CI 0.373–0.649) for P and 0.629 (95% CI 0.601–0.655) for NP (log rank test p= 0.0234). Multivariate analysis ( table below) showed an adverse effect of pregnancy status on survival, independent of stage, grade, age or progesterone receptor (PR) status. Conclusions: Women who are pregnant within two years of diagnosis of breast cancer have higher grade, more locally-advanced tumors and experience a higher mortality than similar women who are never pregnant. Pregnancy persists as a significant adverse survival variable after adjustment for age, grade, stage, and PR status. [Table: see text] No significant financial relationships to disclose.